FIH Study of PFLotus in Persistent Atrial Fibrillation

Background

Catheter ablation with thermal energy sources, including radiofrequency (RF) or cryoablation, is a well-established and effective treatment for atrial fibrillation (AF), demonstrating comparable safety and efficacy in studies where pulmonary vein isolation (PVI) is the procedural endpoint. However, the non-selective diffusion of thermal energy risks collateral damage to adjacent anatomical structures, a limitation for both clinical application and technological advancement. These two catheter types each present distinct trade-offs: point-by-point RF ablation requires considerable operator skill and longer procedure times, while cryoballoon ablation, though more user-friendly, lacks precise spatial control and is less suited for mapping and ablating non-PVI targets.

Pulsed field ablation (PFA) employs high-voltage, ultra-rapid electric fields to induce irreversible electroporation and cellular death. As a non-thermal modality, PFA demonstrates preferential selectivity for cardiomyocytes. This offers the potential to create durable lesions while better preserving surrounding critical structures such as the esophagus, blood vessels, pulmonary veins, and phrenic nerve. Notably, PFA has not been associated with thermal complications like atrioesophageal fistula, phrenic nerve palsy, or pulmonary vein stenosis, suggesting it may enhance PVI effectiveness while reducing procedural risks.

Current evidence for PFA in AF management stems largely from preclinical studies and single-arm clinical trials. Early first-in-human studies with various PFA systems have reported promising outcomes. In the pivotal single-arm PULSED AF trial, PFA (PulseSelect System, Medtronic) for paroxysmal and persistent AF yielded arrhythmia recurrence rates comparable to thermal ablation, with a low rate of primary safety events at one year. The MANIFEST-PF registry reported a 99.9% acute PVI success rate, very low major complications, and reduced atrial arrhythmia recurrence relative to thermal ablation.

A recent randomized controlled trial (RCT) in persistent AF (ADVENT trial) found PFA (Farapulse System, Boston Scientific) non-inferior to conventional thermal ablation for the primary efficacy endpoint-freedom from procedural failure and post-procedural atrial tachyarrhythmias. Another RCT in persistent AF (Sphere-Per-AF trial) confirmed that PFA (Sphere-9 System, Medtronic) was comparable to thermal ablation in both effectiveness and safety, with the added advantage of shorter procedure times.

New catheter designs continue to emerge. The multi-electrode, force-sensing PFA catheter (Globe, Kardium Inc.) was developed as a single-step PVI solution. More recently, a basket-balloon hybrid PFA catheter (Volt™, Abbott) has entered first-in-human trials, with preliminary data supporting its immediate efficacy and safety in persistent AF. A recent meta-analysis concluded that PFA is associated with shorter procedure times but longer fluoroscopy times, while showing no significant differences in complication rates or AF recurrence compared to thermal ablation.

Thus, this first-in-human study aims to evaluate the safety and effectiveness of a novel, PFA catheter that transitions between large 'petals' (single-shot), and a small, spherical 'bud' (large-focal/linear), enabling a PVI-plus strategy in patients with persistent AF (PersAF).

Methods Study Design This was a first-in-human, prospective, single-arm, single-center trial evaluating the safety and efficacy of a novel a novel shape-adaptive PFA ablation catheter in PersAF patients. The study was approved by the local Ethics Committee and conducted in accordance with the Declaration of Helsinki. All participants provided written informed consent.

Study Population Eligible patients were 18-75 years old with documented symptomatic PerAF (AF duration 7-365 days) who were refractory or intolerant to at least one Class I or III antiarrhythmic drug.

Procedural Workflow All procedures were performed under general anesthesia. The activated clotting time was maintained≥300 seconds. A decapolar catheter was positioned in the coronary sinus and a ventricular electrode in the right ventricle. Transseptal puncture was performed under fluoroscopic guidance.

An electroanatomic map of the left atrium and pulmonary veins was created using a PENTARAY® catheter and the CARTO 3 system (Biosense Webster). The PFA sheath was inserted and continuously flushed. The PFLutos catheter was advanced into the left atrium and navigated to target sites.

PVI was performed in all patients. Additional linear ablation strategies Including the left atrial posterior wall (LAPW), mitral isthmus (MI), or cavotricuspid isthmus (CTI), were performed at the operator's discretion. For MI ablation, if persistent epicardial connections were identified, adjunctive ablation within the coronary sinus was performed. After a 20-minute waiting period, isolation and block were reassessed.

Follow-up Post-ablation antiarrhythmic drug use was determined by the operator and typically discontinued after three months. Oral anticoagulation was maintained per guidelines. Structured follow-up occurred at 7 days and 3 months post-ablation, with lesion durability assessed via invasive remapping at 3 months. Additional visits were scheduled at 6 and 12 months. Atrial Tachyarrhythmia recurrence was assessed using 12-lead ECGs at each visit and 24-hour or 7-day Holter monitoring at 3, 6, and 12 months.

Endpoints The primary safety endpoint was the incidence of primary adverse events (PAEs) within 7 days post-ablation. Later-occurring events (device/procedure-related death, atrio-esophageal fistula, PV stenosis) were also classified as PAEs. Persistent diaphragmatic paralysis or phrenic nerve palsy at 3 months were considered PAEs.

The primary efficacy endpoint was acute procedural success, defined as the proportion of patients achieving: 1) complete electrical isolation of all PVs, and 2) for those undergoing linear ablation, confirmed bidirectional block at all targeted sites (LAPW, MI, CTI).

Secondary efficacy endpoints included:

1. Acute PV isolation success rate.

2. Acute success rate of bidirectional block for each linear ablation site.

3. Durable success rate of bidirectional block for each linear ablation site at 3-month remapping.

4. One-year freedom from atrial tachyarrhythmia recurrence.